E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
This charming flower is named from the son of Cephisus. This beautiful youth saw his reflection in a fountain, and thought it the presiding nymph of the place. He tried to reach it, and jumped into the fountain, where he died. The nymphs came to take up the body that they might pay it funeral honours, but found only a flower, which they called Narcissus, after the name of the son of Cephisus. (Ovids Metamorphoses, iii. 346, etc.)
Plutarch says the plant is called Narcissus from the Greek narke (numbness), and that it is properly narcosis, meaning the plant which produces numbness or palsy.